1: the incarnation of a Hindu deity (as Vishnu)
2: a: an incarnation in human form
b: an embodiment (as of a concept or philosophy) often in a person
3: a variant phase or version of a continuing basic entity

Within the cyber-community, however, avatars more generally refer to
the virtual bodies used by people while in cyberspace.

Neal Stephenson is widely credited with first using the term in his 1993
book Snow Crash to refer to an image or 3D figure that represents
a person in cyberspace. However, as Stephenson himself says in the Bantam
paperback edition, after the first publication of Snow Crash I learned
that the term avatar has actually been in use for a number
of years as part of a virtual reality system called Habitat, developed
by F. Randall Farmer and Chip Morningstar. http://hiwaay.net/~crispen/vrml/cyberspace.html

Avatars can be chosen to reflect the identity that the person wishes
to adopt. As Judith S. Donath explains, identity plays a key role
in virtual communities. In the physical world there is an inherent unity
to the self, for the body provides a compelling and convenient definition
of identity. The virtual world is different ... it is composed of information
rather than matter ... one can have, some claim, as many electronic personas
as one has time and energy to create. http://smg.media.mit.edu/people/Judith/Identity/IdentityDeception.html

In cyberspace (or in Stephensons Metaverse) you can make your avatar
look like anything you want. If you're ugly, you can make your avatar
beautiful. If you've just gotten out of bed, your avatar can be wearing
beautiful clothes and professionally applied makeup. You can look like
a gorilla or a dragon

Atmosphere from Adobe is the latest kid on the block when it comes to
3d on the web, and for new users comes ready equipped with eight avatars.
But you dont need to stick with just these, as you can build your
own, or use avatar's created by other people. Read more about Atmosphere
Avatars.